I want a game where the players take on the role of eldritch abominations and elder gods fighting over some world. You would start off weak, perhaps possessing one unlucky bastard or somehow manifesting in the world, and then you build your cult and grow stronger.
In the beginning, you'll probably work together to achieve common goals (set up an international cult, indoctrinate world leaders) and then you hit the apocalypse phase. The apocalypse is the phase of the game where each player is already a world power, and the time is right to reshape the world in his image. To do this, he must defeat the other players in a battle royale. So you'll be flinging nukes all over the place, summon armies of undead, sacrifice entire nations to fuel infernal rituals, all that - so you can rise as the supreme god of the setting and eat the world.
Basically, what starts as a low-level version of Demon: the Fallen ends up becoming Risk and Diplomacy, but with Lovecraftian overlords vying for supremacy.